This invention relates generally to communications and more particularly to third party initiated calls.
Third party call control involves one or more network devices, generally referred to as call controllers, initiating and managing a call between two endpoints. Third party initiated calls are advantageous over endpoint initiated calls because the call controller may provide value-added features such as conference center, which may be used to route a call originating from an IP phone to a 1-800 number to a predetermined call agent.
Other desirable services and features require third party call control, such as Click-to-Dial. Click-to-Dial allows a person to use a webpage to specify a call between two Session Initiation Protocol (SIP) capable devices such as two Internet Protocol (IP) phones, an IP phone and an IP host, or two IP hosts. The user, who may or may not be located at any of the called endpoints, uses the webpage to specify endpoints to be called and then clicks to initiate the call. A web server converts that click to a third party call request. A call controller then initiates a third party call to connect the endpoints upon receiving the request.
FIG. 1 illustrates a third party initiated call between two SIP capable IP phones A and B. Call controller 1 receives a Click-to-Dial request 2 specifying a call between IP phones A and B. Next, call controller 1 exchanges SIP signaling messages 4 with each endpoint according to Request For Comment (RFC) 3725, which is publicly available on the Internet Engineering Task Force (IETF) website. For example, the call controller 1 exchanges SIP signaling messages 4 with IP phone B to determine session information 5 for IP phone B, which is then provided to IP phone A. IP phone A then uses the contact information 5 to establish an IP media path 3 to IP phone B. After the media path 3 is established, IP phones A and B exchange media such as audio or video packets over the media path 3.
However, according to RFC 3725 operation, controller 1 requires that each endpoint understand SIP signaling messages. Plain Old Telephone System (POTS) phones, such as phone C located on the Publicly Switched Telephone Network (PSTN) 98, do not understand SIP. Therefore, third party call control according to RFC 3725 and the accompanying features, such as Click-to-Dial, cannot be used directly with these devices.
In other words, phones A and C can only communicate over an endpoint initiated call 6. Moreover, once the call 6 is initiated, third party call control features such as conferencing and operator services are unavailable for endpoints C. The disclosure that follows solves these and other problems.